In precision sand casting processes for forming an internal combustion engine block, an expendable mold package is assembled from a plurality of resin-bonded sand cores. The sand cores define the internal and external surfaces of the engine block. Resin-coated foundry sand is generally blown into a core box and cured to form the expendable mold package. A typical mold package is shown and described in commonly owned U.S. Pat. No. 6,615,901, hereby incorporated herein by reference in its entirety.
Cast-in-place bore liners are often used with the expendable mold package for engine block castings. Typically, the mold assembly method involves positioning a base core on a suitable surface, and building up or stacking separate mold elements to shape casting features such as sides, ends, a water jacket, cam openings, and a crankcase. Cast iron bore liners are positioned on barrel core features and subsequently become embedded in the engine casting after the metal is poured into the mold.
The engine block casting generally must be further machined so that the cylinder bores formed from the bore liners positioned on the barrel core features have uniform bore liner wall thickness, and that other desired block features are accurately machined. To facilitate the further machining, it is desirable that the liners be precisely and accurately positioned relative to one another within the engine block casting. The ease and consistency with which the bore liners are brought into the desired final position during the mold assembly process is an important consideration.
In barrel slab cores, the bore liners are positioned on the barrel core features by slidingly placing the bore liners over the barrel core features. A known device and method for assembling bore liners onto barrel core features is disclosed in commonly owned U.S. Pat. No. 7,383,874, hereby incorporated herein by reference in its entirety. The mold assembly device includes a magnet for securing a cast-in-place cylinder bore liner during assembly of a mold package, the magnet militating against undesirable movement of the bore liner during assembly of the mold package.
As shown in FIGS. 1 and 2, a typical robotic end-of-arm tool 10 for positioning bore liners into precision sand molds employs at least one permanent magnet 20 and a plurality of ferrous poles 40 disposed within a permanent magnet material handling device 30. The permanent magnets 20 are typically interposed between the poles 40 and are disposed inside of the permanent magnet material handling device 30. The poles 40 typically are coupled to the body of the permanent magnet material handling device 30, such as with bolts and the like, and extend outwardly from the permanent magnet material handling device 30.
The robotic end-of-arm tool 10 with the permanent magnet material handling device 30 is selectively affixed to a bore liner assembly robot that precisely positions the end-of-arm tool 10 as desired, for example, according to one or more programmable subroutines. The permanent magnets 20 have magnetic strength sufficient to secure the bore liners with the poles 40 of the permanent magnet material handling device 30 during assembly. The permanent magnet 20 may be a rare earth magnet, such as a neodymium magnet, for example. Other suitably strong permanent magnets 20 are also employed.
The permanent magnet 20 and the adjacent poles 40 may forcefully attract foreign material, including ferrous objects such as the common wrench and other hand tools which an operator may regularly use near the permanent magnet material handling device 30. The undesirable attraction of loose ferrous objects to the permanent magnet 20 and the poles 40 may create a “pinch point” hazard. Other loose ferrous bodies such as nuts, bolts, screws, and the like, and ferrous foreign material such as scrap, shavings, and the like, may further magnetically adhere to the permanent magnet 20 or the poles 40 and adversely affect the mold package assembly process. An accumulation of foreign material onto the permanent magnet assembly may undesirably result in a misalignment of the bore liner during the assembly process.
There is a continuing need for a reliable apparatus and method of assembling bore liners into precision sand foundry molds that minimizes pinch point hazards. Desirably, the apparatus detects foreign bodies attached to the magnets and militates against possible injury and scrap molds and scrap castings caused by foreign material attached to the magnet.